How to Measure Signal Strength

Cell signals change constantly as new towers are installed by carriers, construction projects become implemented, seasons transition, and as devices age and technology changes, for example. Your signal strength is in constant flux as you transition to different locations and experience a multitude of environmental changes throughout each day.

What about signal bars?

The bars shown in the notification panel of your cell phone are not very accurate. They give you a general idea of your signal strength, but not a quantifiable reading. Carriers can display any number of bars in your notification panel regardless of actual signal strength. You can do more than check your bars to measure signal strength on your cell phone! Here are a few quick tricks that you can use to measure your cell phone signal or get more information on your cellular coverage.

Measure Signal Strength in Numbers (dBm)

Signal strength received from a cell tower is measured in decibel-milliwatts and represented by the unit dBm, which is a unit of electrical power in decibels (dB) in reference to 1 milliwatt (mW). dBm is a more advanced, quantifiable measurement of signal strength.

The scale runs from -150 to 0 dBm, and a number closer to zero indicates stronger cell signal. -50 to -95 dBm is a common, working signal. If your reading is below -95 dBm, say -105 dBm, then you probably have a very weak and unreliable cell signal. My dBm reading is currently -115, which means I probably need a cell booster! If you measure signal strength at -95 dBm and install a cell booster with +30 dB of gain then your signal strength will improve to -65 dBm upon installation. So, how can you measure signal strength in dBm on your phone?


On an Android phone, navigate to Settings > General > About Device > Status > Signal Strength. If you can’t find it in your phone search for ‘about device’ or ‘status’ or ‘SIM status’.

−60 or greater = Excellent
−60 to −75 = Above Average
−76 to −90 = Average
−91 to −100 = Fair
−100 to −110 = Weak
Less than −110 = No Signal

Note: Add +20 dBm to the reading your phone displays because professional meters give readings +20 dBm higher than the figure shown on cell phones.


On an iPhone, open your phone keypad and enter *3001#12345#* then hit the call button and your phone will enter Field Test mode. Once it does, tap the dots next to your signal bars icon. The number might appear even without tapping on the dots.

Measure Signal Strength on iPhone

To save the numerical reading in your status bar, hold down the power button until it gives you the option to power your phone off. Hard press and hold your home/Touch ID button for 10 seconds, which will force close the Field Test mode and redirect you to the home screen. Now your notification panel will always show bars as well as dBm readings! All you need to do to switch between dots and dBm is tap that part of the status bar. If you’re operating on iOS 11 please read this article.

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Consult Coverage Maps

There are a few different maps you can check to measure signal strength and understand the way your cell coverage behaves, and they’re based on information from carriers as well as crowdsourced metrics. CellReception compiles information from networks and users, while OpenSignal, SignalMap, and RootMetrics only use information provided by users. Select a toggle below for more information about each coverage map.

Visit CellReception. Type in your zip code or city and press Go. Check the box for the towers your carrier uses (look up which towers your carrier uses) and the map will update. Zoom in and out to see how many towers are in your coverage area. You can also read reviews of your carrier’s service written by real people living or working in that service area.

Step 1 Enter your location information

Step 2 Select network ratings or towers specific to your location. Sample map shown

OpenSignal is another producer of coverage maps that uses crowdsourced data obtained from users of their mobile apps. Select your location and network, then click View Map. Visit OpenSignal.

Step 1 Enter your location and network information

Sample map image showing signal strength details in central Minnesota

This map was created with crowdsourced information provided by people and not with any input from networks. All you need to do is input or zoom to your address and select your network/carrier to browse maps created by users like you! Visit SignalMap.

Step 1 Enter your location and network details

Sample coverage map showing multiple coverage indicators

This coverage map was crowdsourced by individuals using the service, and not with any information provided by networks. All you need to do is input or zoom to your address and select your network/carrier to browse maps created by users like you! RootMetrics has additional layers to their coverage map that you can experiment with. Visit RootMetrics.

Sample coverage map showing good, fair, poor, bad, and untested signal strength areas

If your coverage map indicates that you should have good service at your location, you could try resetting your phone which could cause your phone to select a better cell tower or try any of these other free solutions to a bad cell signal. Browse the app store on your phone for apps that monitor your connection and provide more information and readings than you probably know what to do with! Measure signal strength for personal use, but it can also be helpful when you need to discuss your coverage problems with your carrier.

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